Thermal printing apparatus



Feb. 10, 1970 M. H. ZISSEN THERMAL PRINTING APPARATUS 2 Sheets-Sheet 1 Filed May 29, 1957 OUT A 26 READ-- DIGITAL llb CO H PA RATOR 4W INPUT FIG.I

HEATER SUPPLY Il II FIG.2

Feb. 10, 1970- M. H. ZISSEN 3395 076 THERMAL PRINTING APPARATUS Filed-May 29, 19s? 2 Sheet s-Sheet 2 Bl: l5b 16b |8b llb FIG.4

United States Patent 3,495,070 THERMAL PRINTING APPARATUS Murray H. Zissen, deceased, late of San Jose, Calif., by Ina M. Zissen, executrix, 3801 Underwood Drive, Apt. 1, San Jose, Calif. 95117 Fiied May 29, 1967, er. No. 643,313 Int. Cl. 1105b 3/28 US. Cl. 219216 3 Claims ABSTRACT OF THE DISCLOSURE Thermal printing apparatus in which thermally sensitive paper is fed to a printing unit containing elongated heating segments which sensitize visual markings on the paper. The heating segments are formed in a la er pattern on a heat-insulating substrate, superimposed on a layer pattern of monitoring segments made of thermistor material. A given combination of the heating segments are energized to produce a desired visual marking with a given distribution of digital current pulses, and the proper functioning of the heating segments is indicated by obtaining the identical distribution in the temperature response of the monitoring segments.

The present invention relates to apparatus for printing electronically processed information on thermally sensitive paper.

It has been previously recognized that the imprinting of digital information on thermally-sensitive paper, for example Thermo-Fax paper manufactured and sold by Minnesota Mining and Manufacturing Co., offers the inherent advantage of high-speed and quiet printing of readout information generated by a digital computer. However, previously proposed devices for this purpose are not entirely satisfactory for practical operation.

One object of the present invention is the provision in a thermal printing element of means for monitoring said printing element to insure that it is operating correctly.

Another object of the present invention is the provision of means for increasing the speed with which a thermal printing element can make a legible imprint on thermally sensitive paper.

Another object of the present invention is the provision of means for protecting a thermal printing element from abrasion and wear caused by the rubbing of ther mally sensitive paper on said element.

Still another object of the present invention is the provision of a simple and practical construction for a thermal printing element.

These and other features and advantages of the present invention will become more apparent upon a consideration of the following description taken in connection with the accompanying drawing, wherein:

FIGURE 1 is a schematic diagram of a thermal printing apparatus in accordance with the present invention;

FIGURE 2 is a top plan view of the printing element in the apparatus of FIGURE 1;

FIGURE 3 is a top plan view of the interconnection pattern of the printing element of FIGURE 2; and

FIGURE 4 is an enlarged cross-sectional view taken along line 4-4 in FIGURE 2.

Referring to the thermal printing apparatus of FIG- URE l, a solid-state printing element has a plurality of thermally-excitable, high-resistance segments 11, 12, 13, 14, 15, 16, 17, 18 and 19, arranging in the illustrated example in a pattern particularly suitable for the printing of arabic numerals. This pattern consists of three rows of end-wise aligned pairs of vertically-extending segments, 13 and 14, 12 and 15, 19 and 17, and three parallel horizontally-extending segments 11, 18 and 3,495,070 Patented Feb. 10, 1970 See 16 positioned at either end and between the middle vertically-extending pairs 12 and 15. A sheet of thermally sensitive paper 21 is fed by guides 22 and 23 over the printing element 10 which imprints legible information thereon by means of the heat generated in the printing segments 11 through 19. It is apparent that the printing segments of printing unit 10 can be arranged in any desired pattern, for example, for alphabetic as well as numeric characters, and that any number of such printing units may be used simultaneously for printing on the paper 21.

A digital input source 24 energizes printing segments 11 through 19 with current pulses programmed to thermally energize particular combinations of these printing segments so as to form geometric patterns representative of particular numerals corresponding to each input, via a plurality of respective connecting leads 11a through 19a. Thermal energization of the printing segments 11 through 19 causes operation monitoring pulses to be transmitted over respective connections 11b through 191). This operation monitoring information is compared in a digital comparator 25 with the input from digital source 24 so that any malfunction in the thermal excitation of the printing segments 11 through 19 results in a deviation between the two inputs to the comparator 25, thereby generating an error signal which is detected by a suitable read-out device 26.

The details of the construction of the printing element 10 are shown in FIGURES 2, 3 and 4. A substrate 30 for the element 10 is made from a material having heatinsulating properties, for example glazed ceramic. A pattern of monitoring segments 11' through 19', having the same configuration as the printing segments 11 through 19 is coated on the substrate 30 (see FIGURE 4). The monitoring segments 11' through 19' are made of a thermistor semiconductor material. Next highly conducting interconnection strips 1112 through 20b, made for example of aluminum, are coated over the monitoring segments 11' through 19, to form an interconnection pattern as shown in FIGURE 3. The spaces in between and above the interconnection strips 11b through 20b are coated with a material 31 characterized by both good thermal conductivity and electrical insulating properties, for example aluminum oxide. After a thin insulating layer of the material 31 is coated over the interconnection strips 11b through 20b, a second set of highly conducting interconnection strips 11a through 20a, having the same pattern as that shown in FIGURE 3 for interconnection strips 11b through 20b, is coated directly over the interconnection strips 111) through 20b. More of the material 31 is then coated between the interconnection strips 11a through 20a. Next the printing segments 11 through 19 are coated directly above, and in the same pattern as, the monitoring segments 11' through 19'. Finally, an outer coating 32 is placed over the printing segments 11 through 19 and the interconnection strips 11a through 20a.

The material forming the printing segments 11 through 19 should preferably have a resistance of 300 ohms or more per unit area at a coating thickness of approximately 2000 A. A suitable material for this purpose is Nichrome. The material forming the interconnection strips 11a through 20a should preferably have a resistance which is at least two orders of magnitude less than that of the printing segments. A suitable material for this purpose is aluminum coated to a thickness of 2000 A.

The over-coating material 32 must have good thermal conductivity so that the heat of the printing segments 11 through 19 is transmitted to the thermally sensitive paper 21 (FIGURE 1), and, moreover, should have a hardness which is at least 50 Rockwell units greater than the thermal material used on the sensitized paper. Aluminum oxide is a suitable over-coating material for this purpose. Under these conditions, the over-coating 32 will protect the thermal printing segments 11 through 19 from wear since the paper will bear against the over-coating 32. To further protect against such wear, the paper guides '22 and 23 can be provided with a mechanical relief so that there will not be an excess amount of stress on either the paper 21 or the printing element 10.

Mounted in the paper entrance guide 22 is a heating system comprising a heater coil 41 energized by a heater supply 42. This system is preferably regulated so that the temperature of the incoming paper is maintained at 60 C. :5 C. Thus the paper coming into contact with the printing element is thermally pre-biased. This decreases the time required for the printing element 10 to make a clearly visible mark on the paper 21 to a value in range of 1 to 10 milliseconds.

The relationship between the pattern of printing segments 11 through 19 and the pattern of interconnecting strips 11a through 19a is such that: the strip 11a makes electrical contact with one end of the segment 11; the strip 12a makes electrical contact with one end of the segment 12; the strip 13a makes electrical contact with one end of the segment 13; the strip 14a makes electrical contact with one end of the segment 14; the strip 15a makes electrical contact with one end of the segment 15; the strip 16a makes electrical contact with one end of the segment 16; the strip "17a makes contact with one end of the segment 17; the strip 18a makes contact with one end of the segment 18; and the strip 19a makes contact with one end of the segment 19. The strip member 20a is shaped so as to contact the opposite end of each of the printing segments 11 through 19. Thus strip member 20a provides a common return for current flowing through the printing segments 11 through 19.

Similarly, the relationship between the pattern of monitoring segments 11 through 19' is such that: the strip 11b makes electrical contact with one end of the segment 11; the strip 12b makes electrical contact with one end of the segment 12; the strip 13b makes electrical contact with one end of the segment 13'; the strip 14b makes electrical contact with one end of the segment 14'; the strip 15b makes electrical contact with one end of the segment 15; the strip 16b makes electrical contact with one end of the segment 16'; the strip 17b makes contact with one end of the segment 17; the strip 18b makes contact with one end of the segment 18'; and the strip 19b makes contact with one end of the segment 19'. The strip member 20b is shaped so as to contact the opposite end of each of the monitoring segments 11' through 19'. Thus strip member 20b provides a common return for current flowing through the monitoring segments 11 through 19'.

In operation, the thermally sensitive paper 21 is fed past the printing element 10 with the temperature-sensitive surface of the paper contacting the thermally-conducting over-coating 32 as seen in FIGURE 4. The current pulses from digital source 24 are fed to the interconnecting strips 11a through 19a, thereby flowing lengthwise through the corresponding printing segments 11 through 19. The resistance of these segments is suflicient to generate enough heat for making a visual mark on the thermally sensitive paper in the shape of the segment which is so energized.

More particularly: to print the numeral 1, current pulses are fed to interconnecting strips 13a and 14a to thereby heat up printing segments 13 and 14; to print the numeral 2, current pulses are fed to strips 16a, 17a, 18a, 13a and 11a to thereby heat up printing segments 16, 17, 18, 13 and 11; to print the numeral 3, current pulses are fed to strips 16a, 17a, 18a, 19a and 11a to thereby heat up printing segments 16, 17, 1'8, 19 and 11; to print the numeral 4, current pulses are fed to strips 14a, 17a, 18a and 19a to thereby heat up printing segments 14, 17, 18 and 19; to print the numeral 5, current pulses are fed to strips 16a, 14a, 18a, 19a, 11a and 13a to thereby heat up printing segments 16, .14, 18, 19, 11 and 13; to print the numeral 6, current pulses are fed to strips 16a, 14a, 13a, 11a, 19a and 18a to thereby heat up printing segments 16, 14, 13, 11, 19 and 18; to print the numeral 7, current pulses are fed to strips 14a, 16a, 17a and 19a to thereby heat up printing segments 14, 16, 17 and 19; to print the numeral 8, current pulses are fed to strips 14a, 16a, 17a, 18a, 13a, 11a and 19a to thereby heat up printing segments 14, 16, 17, 18, 13, 11 and 19; to print the numeral 9, current pulses are fed to strips 18a, 14a, 16a, 17a, 19a and 11a to thereby heat up printing segments 18, 14, 16, 17, 19 and 11; to print the numeral 0, current pulses are fed to strips 16a, 17a, 19a, 11a, 13a and 14a to thereby heat up printing segments 16, 17, 19, 11, 13 and 14.

Whenever one of the strips 11 through 19 is properly energized in accordance with the above program, the heat so generated is conducted through the insulating layer 31 and raises the temperature of the corresponding monitoring strip 11' through 19'. The monitoring strips are made of thermistor material which experiences a large decrease in electrical resistance upon said temperature rise. Thus, if the printing unit 10 is functioning properly, a given distribution of input current pulses on the input strips 11a through 19a results in exactly the same distribution of high conductivity on the output strips 11b through 19b. Suitable conventional circuits are used to transform these pulses of high conductivity into pulses for the comparator 25. Under these conditions, the two inputs to the digital comparator 25 are the same and thus no error signal is registered on the read-out device 26. Conversely, if the printing unit 10 is not functioning properly, the two inputs to the comparator 25 will be difierent and thus the read-out device 26 will register an error signal which may be used to suspend operation until the printing unit 10 is again functioning properly.

It should be noted that the interconnecting strips 11a through 2011 make electrical contact only at the ends of the elongated printing segments 11 through 19, so that a maximum length of current path is established in these segments for advantageously obtaining the maximum temperature rise upon excitation by a digital current pulse. Similarly, the interconnecting strips 11b through 20b make electrical contact only at the ends of the elongated monitoring segments 11' through 19, so that a maximum length of current path is established in these segments for advantageously obtaining the maximum increase in conductivity of these segments when they are heated by the digital pulse temperature rise in the corresponding printing strips 11 through 19.

It is to be understood that modifications and variations of the embodiments of the invention disclosed herein may be resorted to without departing from the spirit of the invention and scope of the appended claims.

Having thus described the invention, what is claimed as new and is desired to be protected by Letters Patent is:

1. A thermal printing device, comprising: a plurality of heating elements adapted to sensitize thermally sensitive paper; and a plurality of temperature responsive elements, one of said elements being in thermal communication with each one of said heating elements, respectively, whereby a given distribution of energization of said heating elements results in the same distribution in the response of said temperature responsive elements to thereby indicate the proper functioning of said heating elements, said temperature responsive elements being formed in a first layer pattern on a heat-insulating substrate; and said heating elements are formed in a second layer pattern on said heatinsulating substrate.

2. A thermal printing device, comprising: a plurality of heating elements adapted to sensitize thermally sensitive paper; and a plurality of temperature responsive elements, one of said elements being in thermal communication with each one of said heating elements, respectively, whereby a given distribution of energization of said heating elements results in the same distribution in the response of said temperature responsive elements to thereby indicate the proper functioning of said heating elements; said temperature responsive elements are formed in a first layer pattern on a heat-insulating substrate; and said heating elements are formed in a second layer pattern on said heat-insulating substrate superimposed on said first layer pattern.

3. A thermal printing device, comprising: a plurality of elongated, high-resistance, heating elements adapted to sensitize thermally sensitive paper; and a plurality of electrical connectors for permitting current to be conducted through any desired combination of said heating elements in order to sensitize said paper in a pattern corresponding to the spatial arrangement of said combination of heating elements, said connectors being disposed to make electrical connection only at the ends of said elongated heating elements, said elongated heating elements being formed in a layer pattern on a heat-insulating substrate, and said connectors being formed in a layer pattern on said substrate, said connector layer pattern being formed so that a separate connector contacts each elongated heating element at one end of said heating element and a single connector contacts all of said elongated heating elements at the opposite end thereof said heating element layer pattern being superimposed over a layer of pattern of temperature responsive elements on said substrate, whereby a given distribution of energization of said heating elements results in the same distribution in the response of said temperature responsive elements to thereby indicate the proper functioning of said heating elements.

References Cited UNITED STATES PATENTS JOSEPH V. TRUHE, Primary Examiner C. L. ALBRITTON, Assistant Examiner US. Cl. X.R. 

